This chapter describes the following three technologies that network designers can use todesign switched LAN internetworks:



LAN switching



Virtual LANs (VLANs)



ATM switching

Evolution from Shared to Switched Networks

In the past, network designers had only a limited number of hardware options whenpurchasing a technology for their campus networks. Hubs were for wiring closets and routerswere for the data center or main telecommunications operations. The increasing power ofdesktop processors and the requirements of client-server and multimedia applications,however, have driven the need for greater bandwidth in traditional shared-mediaenvironments.

Switched Internetwork Solutions

Network designers are discovering, however, that many products offered as switchedinternetwork solutions are inadequate. Some offer a limited number of hardware platformswith little or no system integration with the current infrastructure. Others require completeabandonment of all investments in the current network infrastructure. To be successful, aswitched internetwork solution must accomplish the following:

Offer options to support multimedia applications and other high-demand traffic acrossa variety of platforms.



Provide scalability, traffic control, and security that is at least as good or better thanthat of today's router-based internetworks.



Provide support for embedded remote monitoring (RMON) agent.

3.Ethernet Technologies

Background

The termEthernet

refers to the family of local-area network (LAN) products covered by theIEEE 802.3 standard that defines what is

commonly known as the CSMA/CD protocol. Threedata rates are currently defined for operation over optical fiber and twisted-pair cables:



10 Mbps—10Base-T Ethernet



100 Mbps—Fast Ethernet



1000 Mbps—Gigabit Ethernet

10-Gigabit Ethernet is under development and will likely be published as the IEEE 802.3aesupplement to the IEEE 802.3 base standard in late 2001 or early 2002.

Other technologies and protocols have been touted as likely replacements, but the market hasspoken. Ethernet has survived as the major LAN technology (it is currently used forapproximately 85 percent of the world's LAN-connected PCs and workstations) because itsprotocol has the following characteristics:



Is easy to understand, implement, manage, and maintain



Allows low-cost networkimplementations



Provides extensive topological flexibility for network installation



Guarantees successful interconnection and operation of standards-compliant products,regardless of manufacturer

Ethernet—A Brief History

The original Ethernet was developed as an experimental coaxial cable network in the 1970sby Xerox Corporation to operate with a data rate of 3 Mbps using a carrier sense multipleaccess collision detect (CSMA/CD) protocol for LANs with sporadic but occasionally heavytraffic requirements. Success with that project attracted early attention and led to the 1980joint development of the 10-Mbps Ethernet Version 1.0 specification by the three-companyconsortium: Digital Equipment Corporation, Intel Corporation, and Xerox Corporation.

The original IEEE 802.3 standard was based on, and was very similar to, the Ethernet Version1.0 specification. The draft standard was approved by the 802.3 working group in 1983 andwas subsequently published as an official standard in 1985 (ANSI/IEEE Std. 802.3-1985).Since then, a number of supplements to the standard have been defined to take advantage ofimprovements in the technologies and to support additional network media and higher datarate capabilities, plus several new optional network access control